1. Field of the Invention
This invention relates to a method for transferring patterns on a silicone ladder type resin, and to an etching solution used in such pattern transferring method.
2. Discussion of Background
In recent years, as a method for forming a passivation layer for a solid state element, a stress-relaxing film, or an insulating layer, in the production of semiconductor devices, studies have been made as to a method for spin-coating of high polymer materials having excellent properties such as lower residual stress, better surface smoothness, and higher purity than those of inorganic materials. As the high-polymer materials, there have so far been used thermo-setting resins such as silicone ladder type resins, polyimide resins, and so on having heat-resistance of 450.degree. C. or higher.
When the above-mentioned silicone ladder type resin is used as a passivation layer for a solid-state element, a stress-relaxing layer, or an insulating layer, it becomes necessary to subject these silicone ladder type resin layers to fine machining in order to perforate through-holes for connecting them with the venting portions of the upper and lower conductor layers and with external lead wires.
For the purpose of subjecting a silicone ladder type resin film to fine machining, Japanese Unexamined Patent Publication No. 49540/1981 discloses a wet-type etching process, in which use is made of hydrofluoric acid as the etching liquid. When the present inventors examined workability of this etching liquid, it was found that a silicone ladder type resin could not be etched with hydrofluoric acid.
Also, Japanese Unexamined Patent Publication No. 125855/1981 discloses the dry etching process with use of CF4 gas plasma, which was also found to be disadvantageous in that its etching rate was low, and, in the case of a thick film such as a stress-relaxing layer, a passivation layer, and so on, its etching time was prolonged.
Thus, there has so far been established no technique of stable pattern transfer onto the thick layer of the silicone ladder type resin.